1. Field of the Invention
The present invention generally relates to a core-shell fluorescent material and a light source device using the same, and more specifically to a core-shell fluorescent material comprising a core having yellow, green or red fluorescent powder and a shell having manganese (IV)-doped fluoride compound specified by a chemical formula AxMF6−yZy:Mn4+, such that the core-shell fluorescent material may absorb the blue light to generate white light with high color rendering index.
2. The Prior Arts
In recent years, there has been considerable interest in white light-emitting diodes (wLEDs) owing to their long operation lifetime, low energy consumption, high material stability, and environmentally friendly characteristics. Hence, white LEDs are promising candidate to replace conventional incandescent and fluorescent lamps. One of indispensable materials for manufacturing LEDs is the fluorescent material for light conversion, which is strongly related to LEDs' luminous efficiency, stability, color rendering, color temperature and lifetime, especially for the white light LED system using the integrated single chip.
In general, a white light device needs high color rendering to show the true color of the object. White light can be generated by a combination of blue LED chips coated with the yellow-emitting phosphor Y3Al5O12:Ce3+(YAG:Ce3+) or green-emitting phosphor Lu3Al5O12:Ce3+(LuAG:Ce3+). Nevertheless, the drawbacks of this method include a low-rendering index and high color temperature due to the deficiency of red emission in the visible spectrum.
Therefore, it is greatly needed for a new core-shell fluorescent material with hybrid spectrum and a new light source device using the core-shell fluorescent material. The core-shell fluorescent material can be used as one single fluorescent powder for packaging so as to effectively increase color rendering for white light. The core-shell fluorescent material comprises a core having yellow, green or red fluorescent powder, and a shell having manganese (IV)-doped fluoride compound such that an exciting light with wavelength range of 400-460nm is converted into an emitting light with wavelength in the 520-800nm range. The light source device manufactured by use of the core-shell fluorescent material provides high quality light source, thereby overcoming the above problem in the prior arts.